Everyday use

These use the fonn name. In a checkout without an alias, use node packages/cli/dist/cli/main.js.

fonn                                  # open your default agent
fonn claude                           # open Claude Code
fonn codex                            # open Codex
fonn --profile claude:fable-medium    # pick a profile for this launch
fonn --default codex                  # save Codex as the default, then exit
fonn --filter observe                 # record reductions, deliver full output
fonn --filter-level similar           # also collapse lines that differ only in numbers
fonn --filter off --subagents off     # register no Fonn hooks
fonn help                             # offline help

Pass native arguments after --, for example fonn -- --resume. Flags that override the profile, hooks or permission policy are rejected.

Resume

When a session closes, Fonn prints a command such as fonn resume <launch-id>. It restores the agent, profile, project, filter mode, filter level and subagent preference. If the provider’s session ID was not observed, the same command opens the provider’s session picker.

Read an original back

A shortened observation ends with a footer naming its archived original. Read it in bounded slices:

fonn native-output <launch-id> <artifact-id> --offset 0 --limit 4000

Reads default to 4,000 characters and allow at most 20,000. Continue from the reported next offset.